Non-woven based on exploded or splittable multicomponent fibers

ABSTRACT

A hydro-entangled non-woven based on multi-component fibers, either exploded or splittable by hydro-entangling, and a process for the obtaining of the same is described: the thus obtained non-woven has improved softness, resistance and appearance and increases the productive potential of a future industrial line.

FIELD OF THE INVENTION

The present invention relates to the field of multi-layer non-wovens,which can be used as an absorbent material, particularly in the field ofsurface cleaning, personal hygiene or for the formation of garments.

BACKGROUND OF THE ART

A non-woven is widely used as a replacement for traditional textileproducts in a number of sectors, for example in the field of cleaningand protection of surfaces, or in the production of garments. Comparedto traditional fabrics, the non-woven have the advantage of lowerproduction costs, outstanding mechanical properties and a highbiocompatibility with skin.

Non-wovens are formed by synthetic, natural or naturally-derivedmaterial fibers, which are arranged on a mat in a molten state and leftto solidify in the form of a layer; the thus obtained structure can beconsolidated by dynamic treatments such as point-bonding or calenderingor by water jets (hydro-entangling); other prior art bonding processesare mechanic needling, thermobonding, chemical bonding, etc.

Non-woven fibers generally consist of a single component; however forparticular applications they may also be produced in a multi-componentform, through the joint extrusion of different polymers.

The non-woven fibers are used in the form of single-ply or in the formof multi-layer composites; of the multi-layer composites thosecontaining one or more layers of non-woven, associated to a layer ofcellulose fibers are known: in these cases the final compositeadvantageously combines the non-woven mechanical properties to theabsorbent properties of cellulose fibers.

Unfortunately, the manufacture of these composites entails particularproblems: in fact, the cellulose layer (that is typically formed byshort fibers and is poorly reactive to the entangling processes), isvery mobile and poorly cohesive with the other layers; thereforeproblems of cellulose material loss during the formation of themulti-layer composite are frequent, thus requiring to increase theamount of cellulose fibers used to compensate the losses; besides in thefinal composite one encounters problems of migration of the cellulosefibers thus creating areas that are richer and areas that are poorer inpulp inside the multi-layer non-woven and excessive pulp loss duringhydro-entangling. In addition the cases of composite delamination due toinsufficient entangling between the different layers and between thecontinuous thread fibers on the outer surfaces are frequent. In otherwords, the continuous thread fibers of each of the outer layers ofnon-woven do not entangle suitably either with one another or with thefibers of different layers but rather they protrude from the respectiveouter surfaces in the form of tiny slots. In this way, when a non-wovensheet comes into contact with a rough surface such as a person's hand,the non-woven tends to stick in a bothersome way to the rough surfacedue to miniscule contacts between said slots and the ribs of the roughsurface.

In order to resolve these problems, U.S. Pat. No. 5,587,225 (Griesbachet al.) discloses a composite formed by a cellulose layer interposedbetween two outer non-woven layers, in which the non-woven fibers arenot smooth, but have a series of creases or “crimps” per unit length ofthe fiber. The outer layers are then made integral with the celluloselayer by hydro-entangling, and final fixing of the 3 layers madeadhesively or thermally (calendering). In any case, the crimping andcreasing processes make the composite preparation process longer andmore expensive, and they considerably reduce the softness of theproduct.

WO-A-01/63032 (Orlandi-Fleissner) discloses a multi-layercellulose/non-woven composite wherein the layer of non-woven is cardedand pre-consolidated separately by means of calendering. The differentlayers of the composite are thus overlapped and entangled by means ofhydro-entangling. Also in this case it is necessary to resort toadditional processes of non-woven calendering and pre-consolidation inorder to obtain a multi-layer composite with acceptable performance, andlimit the loss of pulp during hydro-entangling.

Common to all the solutions proposed is the need to perform manyadhesion processes and/or pre-treatment of the fibers in order to obtaina sufficiently cohesive multi-layer product: this entails an increase inprocess time and costs and moreover an excessive rigidity of the finalproduct when additional thermo-welding processes are followed.

SUMMARY

The object of the present invention is therefore to overcome all theinconveniences mentioned with reference to the multi-layer non-wovensobtained according to the state of the art and particularly according tothe processes described above.

This object is achieved by a process for preparing a single- ormulti-layer non-woven and a thus obtained single- or multi-layernon-woven, as detailed in the independent claims appended hereto.

It was surprisingly noted that the use of particular polymer fibers forthe formation of the outer layers of single-layer non-woven allows toresolve the abovementioned drawbacks and advantageously improve thefunctional and tactile characteristics of the product itself.

Particularly, the single- or multi-layer non-woven fabric is of ahydro-entangled type based on exploded continuous thread or splittablemulti-component continuous thread fibers. The thus obtained fabric hasfor example high characteristics of softness and resilience.

By “continuous thread fibers” is meant herein a single continuous fibercomposed of one or more synthetic or natural polymer components that maybe decomposed into single micro-fibers, or filaments, according to thetype of fiber used. Accordingly, both the splittable multi-componentpolymer fibers and the exploded polymer fibers give origin tomicro-fibers, which are thinner than the fibers from which they derive.

DESCRIPTION OF THE FIGURES

Further characteristics and the advantages of the non-woven inaccordance with the present invention will be better understood in thefollowing detailed description of embodiments provided by way ofnon-limiting examples with reference to the appended figures, wherein:

FIG. 1A represents a schematic view of the production line and of themanufacturing steps of the single-layer non-woven;

FIG. 1B represents a schematic view of the production line and themanufacturing steps of three-layer non-woven composite according to thepresent invention;

FIG. 1C represents a schematic view of the production line and themanufacturing steps of a three-layer non-woven composite withpre-hydro-entangling of one layer according to the present invention;

FIG. 2 represents a perspective view of two embodiments of the mat onwhich the fibers according to the present invention are arranged;

FIG. 3 represents a microscope image of a polymer fiber before (3 a) andafter (3 b) the treatment according to the process described in patentapplication WO 00/20178 in the name of Hills, Inc and Fiber InnovationTechnology, Inc.;

FIG. 4A represents a microscope image of the polymer fiber obtained withNanoval technology comprising polypropylene and Fluff Pulp described inpatent application WO 02/052070;

FIG. 4B represents a microscope image of the spun-bond type polymerfiber with a diameter of 2.2 dtex of the continuous thread type and 80g/mt² PES weight;

FIG. 4C represents a microscope image of the polypropylene polymer fiberobtained with Nanoval technology according to the patent application WO02/052070;

FIG. 4D represents a microscope image of the polymer fiber obtained withNanoval technology according to patent application WO 02/052070 withdifferent process parameters that determine a different “explosion”effect, according to one variant of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A first object of the present invention is therefore to provide aprocess for the production of a single- or multi-layer hydro-entanglednon-woven comprising exploded fibers or splittable multi-componentfibers.

A second object of the present invention is a hydro-entangled single- ormulti-layer non-woven, based on exploded fibers or based on splittablemulti-component fibers.

The fiber forming the non-wovens of the present invention is acontinuous fiber and is generally produced by three technologies:

-   a. production of bi-component synthetic polymer fibers    (multisegments), that are can be split with a hydro-entangling    machine;-   b. production of synthetic polymer fibers with explosion effect, for    example polyester, polypropylene, polyethylene (technology known as    “Nanoval” described in patent applications WO-A-02052070 and    DE-A-19929709, incorporated herein for reference);-   c. production of natural fibers with explosion (such as Lyocell,    PLA, etc.) by “Nanoval” technology described above.    1. Production of Splittable Synthetic Polymer Fibers

As for the production of a single layer, as represented schematically inFIG. 1A, the manufacturing steps generally comprise the supply of thenon-woven layer T₁ in the form of fibers by means of a spinneret 1(extruder) coupled up to a conventional suction fan A, ahydro-entangling station 2, a drying station 3 and a rewinding station 4of the hydro-entangled layer into a roll. For the details of each step,reference should be made to the following description with reference toFIGS. 1B and 1C in which the steps with similar names are identical tothose outlined above.

The process for the production of a non-woven, comprises the followingmanufacturing steps;

-   -   a) preparing at least one layer (T₁) of splittable        multi-component polymer fibers;

-   b) hydro-entangling said at least one layer such as to obtain a    non-woven in which the multi-component polymer fibers are split into    mono-component micro-fibers that entangle with one another.

According to one embodiment of the present invention, the processprovides that step a) comprises:

-   -   preparing at least one layer (T₁) of splittable multi-component        polymer fibers;    -   laying at least one layer of absorbent material fibers (T₃) on        said at least one layer (T₁),        whereby the hydro-entangling step b) takes place such as to        obtain a non-woven in which the multi-component polymer fibers        split into mono-component micro-fibers entangling with one        another and with the fibers of the absorbent material.

The production of a multi-layer composite in accordance with the presentinvention (FIG. 1B) generally provides, on the other hand, the supplyingof the first layer of non-woven T₁ by means of a special spinneret 5,one or more stations 6 for the laying of cellulose pulp 60, the layingof a second layer of non-woven fabric T₂ by means of a special spinneret7, hydro-entangling 8, drying 9 and rewinding 10.

Referring to a multi-layer product, it is widely known that splittablemulti-component fibers may be produced through extrusion by spinneretsof polymer materials such as to form continuous fibers, in accordancewith the technology a. identified above. These fibers when exiting fromthe spinnerets are hit by a jet of compressed air that causes theelongation and the electrostatic charging thereof such to cause a mutualrepulsion causing them to fall randomly onto a conveyor belt.

With reference to FIG. 1B, a process for the production of multi-layernon-woven fabric comprising outer layers made with splittable fibersaccording to the abovementioned technology will now be described. In anycase, the subject process comprises the following manufacturing steps:

preparing at least one first layer T₁ of splittable multi-componentpolymer fibers (corresponding to step a) as described above);

laying on said at least one first layer T₁ at least one layer T₃ offibers of absorbent material 60;

laying at least one second layer T₂ of splittable multi-componentpolymer fibers on said at least one layer of fibers of absorbentmaterial 60;

hydro-entangling the layers of fibers obtained after the abovementionedsteps such as to obtain a multi-layer non-woven in which themulti-component polymer fibers are split into individual mono-componentmicro-fibers that entangle with one another and with the fibers of theabsorbent material (corresponding to step b) as described above).

Particularly, splittable multi-component synthetic fibers may be formedfor the separate extrusion of the individual polymers in a molten statein the form of threads 50, 70 that protrude from orifices, of capillarydimensions, of a spinneret 5, 7 and the union thereof below thespinneret. The polymers at the molten state are linked in a single fibercombined by extrusion of the individual polymer threads in directionssuch as to cause the contact thereof and the adhesion thereof, asdescribed in patent U.S. Pat. No. 6,627,025. A suction fan A positionedbelow the spinneret has the function of sucking and conveying theindividual threads of extruded polymer in order to favour the bondingthereof into a single fiber.

The synthetic fibers may be composed of at least two threads of a singlepolymer up to 16 threads of different polymers, be they homopolymers,copolymers or mixtures thereof. The polymers may be selected frompolyesters, polyamides, polyolefins, polyurethane, polyester modifiedwith additives, polypropylene, polyethylene, polypropyleneterephthalate, polybutylene terephthalate.

Preferably, such polymers may be selected such that in the fibersadjacent polymers cannot mix or in any case have poor affinity in orderto favour the subsequent separation thereof. Alternatively, the polymersmay be additized with lubricants that prevent the adhesion thereof. Inaddition, as the longitudinal, axial portion of the fiber usually has agreater force of cohesion than the peripheral portion, it may beadvantageous to spin multi-component fibers such as to leave an axialhole or in any case a weakened axial portion.

As shown in FIG. 1B, once a layer of splittable multi-component polymerfibers has been laid through the special spinneret 5 onto a conveyorbelt S such as to create a first layer of spun-bonded non-woven fabricT₁, one layer of absorbent material T₃ such as cellulose pulp is laid onsaid layer of non-woven fabric.

Subsequently, a second layer T₂ of non-woven fabric substantiallyidentical to that prepared previously is laid on the layer of cellulosepulp T₃, as represented in FIG. 1B by the station identified withreference number 7.

At this point, the fibers are subject to hydro-entangling at thehydro-entangling station 8. This treatment, widely known per se,advantageously enables to split the polymer fibers that compose theouter layers of non-woven in micro-fibers and to entangle them with oneanother and with the cellulose pulp fibers.

Preferably, the hydro-entangling is made not only on side S₁ of thesupport S on which the fibers are laid but also on side S₂, oppositeside S₁, through special through holes (not shown in the figures) andsuitable equipment positioned on said side S₂ (not shown).

FIGS. 1B and 1C also schematically represent a conventional filteringdevice 20 for the water originating from the hydro-entangling machinespositioned after the cellulose pulp laying step. Said device has thefunction of recovering the water of the hydro-entangling machine andfiltering it of any cellulose pulp fibers.

FIG. 3 shows the splittable multi-component polymer fiber before (3 a)and after(3 b) the hydro-entangling treatment.

Further examples of splittable multi-component fibers are described inpatent applications U.S. Pat. No. 5,970,583, DE-A-19846857 and WO00/20178, incorporated herein for reference.

It is understood that with this treatment the free spaces between thepolymer fibers laid on the conveyor belt are considerably reduced.Therefore, there is less cellulose pulp loss during hydro-entangling. Itresults that a greater amount of cellulose pulp may be withheld in thefinal multi-layer product with a resulting considerable increase in theabsorbent power and softness and with advantages of reduction ofcellulose pulp loss in the abovementioned filtering system.

2. Production of Exploded Synthetic Polymer Fibers

The process for the production of non-woven based on exploded polymerfibers comprises the following manufacturing steps:

-   i) preparing at least one layer (T₁) of exploded polymer fibers;-   ii) hydro-entangling said at least one layer such as to obtain a    non-woven fabric in which the polymer fibers are exploded into    micro-fibers entangling with one another.

Preferably, the step i) comprises:

preparing at least one layer (T₁) of exploded polymer fibers;

laying at least one layer of fibers of absorbent material (T₃) on saidat least one layer (T₁), whereby the hydro-entangling step ii) takesplace such as to obtain a non-woven fabric in which the polymer fibersexploded into micro-fibers entangle both with one another and the fibersof the absorbent material.

More preferably, the step i) comprises:

-   -   preparing at least one layer (T₁) of exploded polymer fibers;    -   laying on said at least one layer (T₁) at least one layer of        fibers of absorbent material (T₃);    -   laying at least one further layer (T₂) of exploded polymer        fibers on said at least one layer of fibers of absorbent        material,        whereby the hydro-entangling step ii takes place such as to        obtain a multi-layer non-woven fabric in which the polymer        fibers exploded into single micro-fibers entangle with one        another and with the fibers of the absorbent material.

According to Nanoval technology, the explosion of the fiber (justextruded at the molten state) is obtained when it comes into contactwith air at room temperature.

Generally, as described in patent application WO 02/052070, Nanovaltechnology consists in producing molten polymer threads protruding fromspinning holes arranged in one or more rows placed in a chamber with agiven pressure value separated from the outside environment and filledwith gas, generally air. Said threads come to an area of rapidacceleration of this gas when exiting from the camera, the outlet beingmade in the form of a Laval nozzle.

The forces that are transmitted to the respective threads along theroute, following tangential stress, increase, while the diameter of thethreads drops strongly and the pressure in their still fluid innerportion increases intensely in an inversely proportionate manner to theeffect of surface stress. Following the acceleration of the gas,pressure drops according to hydrodynamic laws. Besides, the temperatureconditions of the molten mass, the gas flow and the rapid accelerationthereof adapt with one another, so that the thread before being curedreaches an inner hydrostatic pressure which is greater than the pressureoutside the chamber, whereby the thread explodes into a plurality ofmicro-fibers or fine filaments. Through a slit in the bottom of thechamber, both the threads and the air can be released from the chamber.

The raw materials that can be spun are both of natural origin, such ascellulose Lyocell, PLA, and synthetic or such as polypropylene,polyethylene, polyamide, polyester.

Alternatively, the spinning mass is forced through a elongated nozzle inthe form of a slit into a chamber separated from the environment with agiven pressure, as above, into which gas, for example air, isintroduced. The film that is released from said nozzle reaches an areaof rapid acceleration of the gas released from said camera. Below theacceleration area, i.e. in the stress release area, the film explodesand substantially endless micro-fibers or filaments are obtained. In anycase, unlike those formed by single threads, they have very differentdiameters and thickenings in the shape of knots.

Preferably, the Laval nozzle is cylindrical and elongated with aconvergent edge so that the transversal section thereof is narrowupstream and then rapidly widens downstream. In the narrowest portion,by selecting the pressure value in the chamber (in the case of air abouttwice environmental pressure), flow speeds near to those of sound areobtained whereas in the wider part of the Laval nozzle speeds are higherthan those of sound.

It is understood that a man skilled in the art will be able to set theworking parameters for example, the flow rate of the polymer melted inthe spinneret, the temperature inside said spinneret and the gas flowrate in order to adapt them to the type of polymer used and to thespecific requirements for obtaining diameters of the individualmicro-fibers or filaments.

With regards to the laying of the exploded fibers to form a first layerand the further manufacturing steps, the same references are valid asmade to FIGS. 1A, 1B and 1C in which the suction fan A is eliminated andthe spinnerets 5, 7, 11, 15 are each fitted with the abovementionedLaval nozzle (not shown) in order to obtain the explosion effect.

The advantage of use of the Nanoval technology lies in the possibilityof producing very fine micro-fibers with diameters of less than 10 μm,for example between 2 and 5 μm in a simple and cost effective waywithout the aid of jets of gas (air) heated beyond the polymer's meltingpoint, as occurs for example with meltblown technology. Besides, themicro-fibers are not damaged in their molecular structure by the use ofhigh temperatures. Accordingly, the end product has greater resistanceand therefore shows slower wear over time.

A further advantage also in relation to the technology that employssplittable polymer fibers lies in the fact that a greater density ofindividual micro-fibers per each fiber is obtained. In other words thefiber divides into a number of components with equal initial diameters,i.e. the micro-fibers (filaments) that are obtained are at least 10times finer, preferably up to 100 times finer.

Regardless of the type of splittable or exploded fiber used, if it isdesired to pre-hydro-entangle the non-woven before bonding it into theform of a multi-layer composite (FIG. 1C), the steps are as follows:laying the first layer T₁ by means of the spinneret 11,pre-hydro-entangling through equipment 12, drying through equipment 13,laying cellulose pulp T₃ through equipment 14, laying the second layerT₂ through spinneret 15, hydro-entangling with hydro-entangling machine16, drying through equipment 17 and rewinding onto a roller 18. Theproduction process and system may also provide a dewatering step orstation 19 associated to the drying step or station. The advantage of apre-hydro-entangling step is that it allows to create a first layer ofsplit or exploded polymer fibers that, thanks to the greater density ofthe entangling of the micro-fibers of said fiber, helps to lay fibers ofabsorbent material and prevents the partial loss thereof through spacestoo wide, which are left by prior art technologies.

As mentioned previously, the step of laying fibers of absorbent materialis preferably made with cellulose pulp fibers having a length that mayvary from 0, i.e. cellulose powder, to 2.5 mm, preferably from 1 to 2mm.

In addition, the process according to the invention may provide a dryingstep after the hydro-entangling step and, preferably also after thepre-hydro-entangling step.

A further step may consist in the elimination of the water contained inthe fibers by means of a dewatering step. Particularly, said stepconsists in arranging a condenser 19 below support S for the non-wovenfibers to which a completely conventional suction fan (not shown) isusually coupled up. The air sucked through the holes made on saidsupport is conveyed into said condenser where it releases the watercontained therein. Equipment of this type is described for example inpatent application PCT/IT2004/000127 of the same applicant.

The process may also comprise an embossing step of the multi-layernon-woven. Particularly, the embossing may consist in a calenderingtreatment made by making the non-woven being heated and pass underpressure between a pair of engraved rollers, in accordance withconventional techniques, or through a further step in a hydro-entanglingmachine. It should be noted that the term “embossing step” does not meana consolidation of the non-woven as occurs according to the prior artmentioned previously but simply constitutes a step enabling to makecaptions and/or three dimensional drawings in order to personalize ordecorate the non-woven through a “thermoembossing” or “hydroembossing”calender.

Preferably, the process comprises sucking the air at room temperaturethrough the abovementioned through holes (non shown in the drawings)made in the support S for the fibers. In this way, the splittable orexploded polymer fibers, laid at the molten state, are cooled and cured.In the case in which exploded fibers are used a humidifier (not shown)can be arranged, which humidifies the exploded fibers immediately beforelaying them on the support S either to help or improve the softness ofthe end product.

Even more preferably, said process may comprise one or more of thefollowing final steps, known per se, in order to increase or addadditional characteristics to the end product: coloring or finishing ofa chemical nature as the anti-pilling treatment and the hydrophiletreatment, antistatic treatment, improvement of flame proof properties,substantially mechanical treatments such as napping, sanforizing,emerizing.

In addition, the non-woven may be subject to a further process ofmulticolor printing using the equipment described in patent applicationPCT/IT2004/000127 of the same applicant. In this case, a sheet ofnon-woven at the end of the process described above, may be printeddirectly in-line following the steps of:

providing equipment for printing of non-woven comprising a movingsupport for the transport of said non-woven and at least one movingprint organ;

providing said equipment with said sheet of non-woven;

performing the printing on said non-woven under the command and controlof a command and control unit, in which said command and control unit isoperatively connected with said support and at least one printing organin order to detect electrical signals originating from said support andat least one print organ, transforming said signals into numericalvalues representative of the state of their angular speed and torsionalmoment, comparing said numerical values with ratios of preset numericalvalues of said angular speeds and torsional moments and sending signalsto said support and at least one print organ in order to correct anyvariation of said values that fall outside said ratios.

Finally, the process in accordance with the present invention maycomprise a step of winding the non-woven on to a roller 18.

It must be considered that a “crimp” effect can be advantageouslyobtained avoiding the use of engraved calenders or machines formechanical “crimping”, by simply laying all the fibers that compose themultilayer non-woven on a support (FIG. 2A and 2B) having a surfacecomprising at least one section with a substantially perpendicularprofile to the vertical flow of laying of said fibers interspaced by atleast one section with an inclined profile of 10°-50° in relation tosaid vertical flow. Obviously the profile of the support may be modifiedsuch as to create geometrical forms or figures and captions in relief asdesired.

The process of the present invention enables to obtain different typesof product:

A. single-layer fabric with basic weight of between 15 and 150 cm/m².The manufacturing process is such as illustrated in FIG. 1A. The fiberused may be either a synthetic fiber with explosion effect, as describedabove and obtained according to the Nanoval technology, or it may be abi-component (multisegments) synthetic fiber, splittable with ahydro-entangling machine, or a natural fiber with explosion (forexample, Lyocell, PLA, etc.), also produced with “Nanoval”.

B. multi-layer fabric with single-layer hydro-entangling or threehydro-entangling steps with pre-hydro-entangling. The product may forexample be a three-layer multi-layer one, of which has one centralcellulose pulp layer and the outer layers have different combinations ofthe technologies illustrated above.

I. Splittable Multi-Component Polymer Synthetic Fibers

Preferably, the splittable multi-component polymer fibers are composedof micro-fibers or filaments of polymer such as those described abovewith reference to the manufacturing process. The micro-fibers may have adiameter of between 0.1 dTex and 0.9 dTex and the corresponding fibersmay vary according to the number of micro-fibers composing it butgenerally their size ranges between 1.7 dTex and 2.2 dTex. The number ofmicro-fibers in said fibers generally ranges between 2 and 16.

Referring to a three-layer non-woven having an inner layer of cellulosepulp fibers and two outer layers of polymer fibers consisting of twodifferent splittable polymer components such aspolypropylene/polyethylene, analytical tests have shown the followingphysical characteristics:

-   -   weight in grams per square meter ranging between 50 and 70,        preferably between 55 and 65;    -   tensile strength in the machine direction expressed in Newton        per 5 cm (N/5 cm) between 50 and 150, preferably between 60. and        120, whereas in the cross-direction between 20 and 75, it is        preferably between 30 and 65;    -   elongation, calculated as a percentage of the length in a        relaxed state, ranged between 35% and 85% in machine direction        (MD), preferably between 45% and 75%, whereas it ranged between        70% and 100% in the cross-direction (CD), preferably between 80%        and 90%;    -   final content of the cellulose pulp fiber ranged between 50% and        75% of the total weight of the non-woven;    -   power of absorption calculated as a percentage of total weight        in relation to the weight of the dry non-woven was between 600%        and 700% (according to the percentage of pulp in the end        product).        II. Exploded Polymer Synthetic Fibers

Referring to the exploded fibers, it was observed that the micro-fibers(filaments) have a diameter ranging between 1 micron and 5 micron,preferably between 2 and 4 micron. Obviously said values may varyaccording to the type of preset characteristics for the end product andwill depend on the production parameters selected, as described above,and in any case known to a man skilled in the art.

As to a three-layer non-woven having one inner layer of cellulose pulpfibers and two outer layers of polymer fibers consisting of a singleexploded polymer component, analytic tests showed the following physicalcharacteristics given in the table: Total Weight of Pulp Weight of MDTensile CD Tensile weight upper layer weight lower level strengthstrength Thickness (grams) (g/m²) (g/m²) (g/m²) (N/5 cm) (N/5 cm) (cm)48-65 11-13 26-39 11-13 18-27 7-14 0.40-0.65

Regardless of the type of polymer fibers used, the final thickness ofthe multi-layer non-woven advantageously reaches values of up to 0.65 mmand a tensile strength of 27 N/5 cm.

It was observed that the non-wovens that are obtained by employing thetechnology relating to the exploded fibers advantageously enable to makea product that is softer and has a better appearance with regards to thecompactness and evenness compared to a product obtained with splitfibers, albeit of good quality. In addition it was noted that thefiltering of the water originating from hydro-entangling is alsoimproved, i.e. it contains fewer cellulose pulp fibers.

The products obtained according to the present invention have a plus ofresistance, softness and have a better appearance. Besides the thicknessis increased either by the explosion effect (Nanoval technology), or(splittable fibers) by the split effect, and by a technology of layingcontinuous thread fibers on the mat: the type of the mat (not smooth)may be as illustrated in FIG. 2.

Particularly, the abovementioned characteristics result from thecombination of the use of splittable multi-component polymer fibers orof exploded polymer fibers in a process of hydro-entangling to obtain amulti-layer non-woven.

In fact as mentioned above, it was surprisingly found that despite thefinal structure of the non-woven being the result of a close weave ofmicro-fibers or fine filaments composing the polymer fibers, thehydro-entangling process is not substantially altered and, at the sametime, it allows to obtain hand and functional characteristics betterthan any multilayer non-woven obtained with prior art technologies.

The weave of the micro-fibers or the individual filaments of the polymerfibers allows to withhold a greater amount of cellulose pulp fibers thusincreasing both the thickness of the end product and the absorbentcapacity thereof. Besides it is understood that at the same time, duringthe hydro-entangling process the loss of cellulose pulp is generallyreduced by 50% compared to the usual technologies and, in the case ofprocess according to the technology described in patent applicationWO-A-01/63032, the loss is substantially identical to the advantage of aproduct considerably better from the point of view of the softness,thickness and homogeneity.

The weave of said micro-fibers also considerably increases the bondingpoints per surface unit so that the resistance is far greater thansingle- or multi-layer products in which whole fibers arehydro-entangled.

As stated in the introductory part of this description, the drawback ofthe bothersome “pilling” effect is also overcome thanks to the highnumber of weaves between filaments, far finer than the whole fibers, theabovementioned tiny slots do not form.

In addition, the process of the present invention advantageously allowsto eliminate the lengthy and costly steps of adhesion and/orpre-treatment of the fibers according to the prior art in order toobtain a sufficiently cohesive multi-layer product.

Below is a non-limiting example of one embodiment of the processaccording to the present invention.

EXAMPLE

In an extruder a 13% cellulose solution is placed in an NMMO(N-methylmorpholin-N-oxide) aqueous solution of 75% and 12% of water ina spinning device consisting of a spinneret with a hole and a roundLaval nozzle, in which the single spinning hole has a diameter of 0.5mm. The solution was introduced directly through pumps in a dosed way ina spinning device. The temperature of the Lyocell spinning mass exitingthe extruder was set at 94° C. On the lower part of the tip of thenozzle and electrical resistance was applied. The elongation of thefiber filaments of the exiting fibers the nozzle was made with air atroom temperature of approximately 22° C. and at a pressure, measuredbefore the acceleration in the nozzle of Laval, between 0.05 and 3 barabove atmospheric pressure. The spinning speed is about 500 m/min. Thefibers exiting the spinneret undergo an explosion effect, caused by thedifference of temperature and pressure between the process of extrusionand spinning and room temperature, thus opening into numerous threadsthat are hit by humidified air by means of a humidifier that causesmoist air containing about 5% of water to pass through the extrudedthreads. After humidification and next to the spinneret, the threads ofthe exploded polypropylene fibers are sucked onto a conveyor belt whichis perforated and has its surface covered with cubical shaped ribs. Thesuction takes place through a fan positioned below said conveyor beltand in correspondence with the spinneret. At this point, the explodedfibers are arranged on said support in the form of a first continuouslayer in amount of 11.5 g/m². Then, said layer is subject tohydro-entangling by means of a device sold by FLEISSNER and equippedwith five sequential injectors mounted on special rollers on bothsurfaces of said support. Said injectors work at respective pressures of15, 50-100-100-100-150 bar and have a diameter of the injection holefrom 100 to 140 microns. Subsequently, said pre-water-entangled layerpasses under a cellulose pulp fiber laying station. The laying of thecellulose fibers takes place through a device sold by FLEISSNER of the“air-laid” type in which the fibers laid are fibers with a diameter of 3micron and laid in amounts of 37.25 g/m². Subsequently, a further layerof exploded polypropylene fibers is laid on said layer of cellulose pulpfibers in the same way as described with reference to the first layer ofexploded fibers. At this point, the three layers are interconnectedthrough hydro-entangling by means of a device identical to thatdescribed previously and at the same conditions. At the end of thehydro-entangling process, the thus formed three-layer non-woven passesinside a drying station in which a perforated drum receives andtransports the non-woven being hit by a hot air flow of approximately120° C. When exiting from the dryer, the non-woven is wound on a windingroller. The feeding speed of the conveyor belt along the whole non-wovenmanufacturing steps is maintained at approximately 500 m/min. The endproduct obtained has the following physical characteristics: TotalWeight of Pulp Weight of MD Tensile CD Tensile weight upper layer weightlower layer strength strength Thickness (grams) (g/m²) (g/m²) (g/m²)(N/5 cm) (N/5 cm) (cm) 60.25 11.50 37.25 11.50 21.93 8.01 0.58

As may be appreciated from what described above, the present patentapplication provides a process for the production of a multi-layernon-woven and a non-woven obtainable with said process that allows toovercome the drawbacks mentioned in the introductory part with referenceto the prior art.

Besides, a man skilled in the art may perform numerous modificationsboth to the process and to the non-woven all being within the scope ofprotection of the claims appended herein.

1. A process for the production of a non-woven, comprising the following manufacturing steps; a) preparing at least one layer (T₁) of splittable multi-component polymer fibers; b) hydro-entangling said at least one layer such as to obtain a non-woven where the multi-component polymer fibers are split into mono-component micro-fibers entangling with one another.
 2. The process according to claim 1, wherein step a) comprises: preparing at least one layer (T₁) of splittable multi-component polymer fibers; laying at least one layer of fibers of absorbent material (T₃) on said at least one layer (T₁), whereby the hydro-entangling step b) takes place such as to obtain a non-woven where the multi-component polymer fibers which are split into mono-component micro-fibers entangle both with one another and the fibers of the absorbent material.
 3. The process according to claim 1, wherein step a) comprises: preparing at least one layer (T₁) of splittable multi-component polymer fibers; laying at least one layer of fibers of absorbent material (T₃) on said at least one layer (T₁); laying at least one further layer (T₂) of splittable multi-component polymer fibers on said at least one layer of fibers of absorbent material, whereby the hydro-entangling step b) takes place such as to obtain a multi-layer non-woven where the multi-component polymer fibers are split into individual mono-component micro-fibers entangling both with one another and the fibers of the absorbent material.
 4. The process according to claim 1, wherein said step a) is made through separate extrusion of at least two polymers by a suitable spinneret (5,7,11,15) below which said at least two polymer components are linked such as to form a single splittable multi-component fiber.
 5. The process according to claim 4, wherein said splittable multi-component fiber is obtained by spinning and subsequently linking up to 16 continuous threads of different polymers.
 6. The process according to claim 1, wherein said polymer fibers derive from at least two threads of a single polymer up to 16 threads of different polymers, be they homopolymers, copolymers or mixtures thereof.
 7. The process according to claim 6, wherein said polymers are selected from polyesters, polyamides, polyolefins, polyurethane, polyester modified with additives, polypropylene, polyethylene, polypropylene terephthalate, polybutylene terephthalate.
 8. The process for the production of a non-woven, comprising the following manufacturing steps; i) preparing at least one layer (T₁) of exploded polymer fibers; ii) hydro-entangling said at least one layer such as to obtain a non-woven where the polymer fibers are exploded into micro-fibers entangling with one another.
 9. The process for the production of a non-woven according to claim 8, wherein step i) comprises: preparing at least one layer (T₁) of exploded polymer fibers; laying at least one layer of fibers of absorbent material (T₃) on said at least one layer (T₁), whereby the hydro-entangling step ii) takes place such as to obtain a non-woven fiber where the polymer fibers exploded into micro-fibers entangle both with one another and the fibers of the absorbent material.
 10. The process according to claim 8, wherein step i) comprises: preparing at least one layer (T₁) of exploded polymer fibers; laying at least one layer of fibers of absorbent material (T₃) on said at least one layer (T₁); laying at least one further layer (T₂) of exploded polymer fibers on said at least one layer of fibers of absorbent material, whereby the hydro-entangling step ii) takes place such as to obtain a multi-layer non-woven in which the polymer fibers exploded into individual micro-fibers entangle both with one another and the fibers of the absorbent material.
 11. The process according to claim 8, wherein the exploded polymer fibers are obtained through the passage of polymer fibers through a Laval nozzle.
 12. The process according to claim 8, wherein the polymers of the exploded fibers are selected from natural or synthetic polymers.
 13. The process according to claim 12, wherein the natural polymers are selected from cellulose, Lyocell and PLA, whilst the synthetic polymers are selected from polypropylene, polyethylene, polyamide and polyester.
 14. The process according to claim 2, wherein said laying of absorbent material fibers takes place with cellulose pulp fibers.
 15. The process according to claim 9, wherein said laying of absorbent material fibers takes place with cellulose pulp fibers.
 16. The process according to claim 1, further comprising a drying step after the hydro-entangling step.
 17. The process according to claim 8, further comprising a drying step after the hydro-entangling step.
 18. The process according to claim 16, further comprising a step of winding the non-woven fabric onto a roller after said drying step.
 19. The process according to claim 17, further comprising a step of winding the non-woven fabric onto a roller after said drying step.
 20. The process according to claim 2, further comprising a pre-hydro-entangling step after said step of preparing at least one layer (T₁) of polymer fibers.
 21. The process according to claim 9, further comprising a pre-hydro-entangling step after said step of preparing at least one layer (T₁) of polymer fibers.
 22. The process according to claim 20, further comprising a drying step after said pre-hydro-entangling step.
 23. The process according to claim 21, further comprising a drying step after said pre-hydro-entangling step.
 24. The process according to claim 16, further comprising a dewatering step simultaneous or subsequent to said drying step.
 25. The process according to claim 17, further comprising a dewatering step simultaneous or subsequent to said drying step.
 26. The process according to claim 18, further comprising a thickening step before the winding step.
 27. The process according to claim 19, further comprising a thickening step before the winding step.
 28. The process according to claim 26, wherein said thickening step takes place through calendering or hydro-entangling.
 29. The process according to claim 27, wherein said thickening step takes place through calendering or hydro-entangling.
 30. The process according to claim 1, wherein air is sucked at a temperature equal to or lower than room temperature through said polymer fibers in order to cool and cure them.
 31. The process according to claim 8, wherein air is sucked at a temperature equal to or lower than room temperature through said polymer fibers in order to cool and cure them.
 32. The process according to claim 8, wherein said exploded fibers are humidified before being hydro-entangled.
 33. The process according to claim 1, further comprising a non-woven finishing step.
 34. The process according to claim 8, further comprising a non-woven finishing step.
 35. The process according to claims 1, further comprising a multicolor printing step of the non-woven.
 36. The process according to claims 8, further comprising a multicolor printing step of the non-woven.
 37. The process according to claim 2, wherein each preparation step of the polymer fibers and laying of the fibers of absorbent material is made on a support (S) having a surface comprising sections with a profile substantially perpendicular to the vertical laying flow of the fibers interspaced by sections with an inclined profile of 10°-50° in relation to said vertical flow.
 38. The process according to claim 9, wherein each preparation step of the polymer fibers and laying of the fibers of absorbent material is made on a support (S) having a surface comprising sections with a profile substantially perpendicular to the vertical laying flow of the fibers interspaced by sections with an inclined profile of 10°-50° in relation to said vertical flow.
 39. A hydro-entangled single- or multi-layer non-woven which is obtainable according to the process in accordance with claim
 1. 40. A hydro-entangled single- or multi-layer non-woven which is obtainable according to the process in accordance with claim
 8. 41. The non-woven fabric according to claim 39, comprising at least one micro-fiber layer.
 42. The non-woven fabric according to claim 40, comprising at least one micro-fiber layer.
 43. The non-woven fabric according to claim 41, wherein said micro-fibers have a diameter of between 0.1 dTex and 0.9 dTex.
 44. The non-woven fabric according to claim 42, wherein said micro-fibers have a diameter of between 0.1 dTex and 0.9 dTex.
 45. The non-woven according to claim 43, wherein said micro-fibers have a diameter of between 1 and 5 micron.
 46. The non-woven according to claim 44, wherein said micro-fibers have a diameter of between 1 and 5 micron.
 47. The non-woven according to claim 45, wherein the weight in grams per meter is between 50 and 70, the tensile strength in the machine direction expressed in Newton per 5 cm (N/5 cm) is between 50 and 150, whereas in the cross-direction of between 20 and 75, the elongation calculated as a percentage in relation to the length in a relaxed state is between 35% and 85% in machine direction (MD), whereas it is between 70% and 100% in the cross-direction (CD), the final content of the cellulose pulp fiber is between 50% and 75% by weight of the total weight of the non-woven, the absorption power calculated as a percentage of the total weight of the weight of the dry non-woven is between 600% and 700%.
 48. The non-woven according to claim 46, wherein the weight in grams per meter is between 50 and 70, the tensile strength in the machine direction expressed in Newton per 5 cm (N/5 cm) is between 50 and 150, whereas in the cross-direction of between 20 and 75, the elongation calculated as a percentage in relation to the length in a relaxed state is between 35% and 85% in machine direction (MD), whereas it is between 70% and 100% in the cross-direction (CD), the final content of the cellulose pulp fiber is between 50% and 75% by weight of the total weight of the non-woven, the absorption power calculated as a percentage of the total weight of the weight of the dry non-woven is between 600% and 700%.
 49. The non-woven according to claim 45, wherein said non-woven is of a three-layer type having a total weight in grams of between 48 and 65, a weight of the upper layer in grams per square meter of between 11 and 13, a weight of the inner layer of cellulose pulp fiber of between 26 and 39 grams per square meter, a weight of the lower layer in grams per square meter of between 11 and 13, a MD tensile strength of between 18 and 27 N/5 cm, a CD tensile strength of between 7 and 14 N/5 cm and a thickness of between 0.40 and 0.65 mm.
 50. The non-woven according to claim 46, wherein said non-woven is of a three-layer type having a total weight in grams of between 48 and 65, a weight of the upper layer in grams per square meter of between 11 and 13, a weight of the inner layer of cellulose pulp fiber of between 26 and 39 grams per square meter, a weight of the lower layer in grams per square meter of between 11 and 13, a MD tensile strength of between 18 and 27 N/5 cm, a CD tensile strength of between 7 and 14 N/5 cm and a thickness of between 0.40 and 0.65 mm.
 50. Use of splittable or exploded multi-component polymer fibers for the production of a single- or multi-layer non-woven.
 51. The use according to claim 50, wherein said multi-layer non-woven comprises one layer of absorbent material fibers between two layers of split or exploded multi-component polymer fibers. 